Vitamin D for Muscle Function

Research suggests that vitamin D plays a meaningful role in skeletal muscle function, with a 2023 systematic review finding consistent evidence across cell, animal, and human studies that vitamin D supports muscle cell growth, structural integrity, and recovery, and linking deficiency to reduced muscle strength and slower gait particularly in older adults. Studies indicate that the picture becomes more complicated in specific populations, however, as large randomized controlled trials in children found that correcting severe vitamin D deficiency through supplementation did not translate into measurable improvements in grip strength, explosive power, or cardiorespiratory fitness, and international clinical practice guidelines for sarcopenia concluded that evidence was insufficient to support a formal recommendation for vitamin D supplementation as a treatment. A 2019 review reinforced this tension, noting that while laboratory and observational research strongly implies extraskeletal roles for vitamin D including in muscle function, results from randomized controlled trials remain inconsistent. Overall, the body of evidence is mixed in direction and varies by population, outcome measured, and study design, suggesting that vitamin D may support muscle health under certain conditions — particularly in deficient or older individuals — but that its broader therapeutic value for muscle function has not yet been firmly established.